Workpieces, including food products, are cut or otherwise portioned into smaller portions by processors in accordance with customer needs. Also, excess fat, bone, and other foreign or undesired materials are routinely trimmed from food products. It is often desirable to portion and/or trim the workpieces into uniform sizes, for example, for steaks to be served at restaurants or chicken fillets used in frozen dinners or in chicken burgers. Much of the portioning/trimming of workpieces, in particular food products, is now carried out with the use of high-speed portioning machines. These machines use various scanning techniques to ascertain the size and shape of the food product as it is being advanced on a moving conveyor. This information is analyzed with the aid of a computer to determine how to most efficiently portion the food product into optimum sizes. For example, a customer may desire chicken breast portions in two different weight sizes, but with no fat or with a limited amount of acceptable fat. The chicken breast is scanned as it moves on an infeed conveyor belt and a determination is made through the use of a computer as to how best to portion the chicken breast to the weights desired by the customer, so as to use the chicken breast most effectively.
Portioning machines of the foregoing type are known in the art. Such portioning machines, or portions thereof, are disclosed in prior patents, for example, U.S. Pat. Nos. 4,962,568 and 5,868,056, which are incorporated by reference herein. As typical, the portioning machine includes an infeed conveyor having a moving, solid belt that slides over a support structure. The infeed conveyor belt is driven at a selected speed by a drive motor. The drive motor can be composed of a variable speed motor to thus adjust the speed of the infeed belt. The workpieces are first carried by the infeed conveyor past a scanning station, whereat the workpieces are scanned to ascertain selected physical parameters, for example, their size and shape, and then determine their weight, typically by utilizing an assumed density for the workpieces. In addition, it is possible to locate discontinuities (including voids), foreign material, and undesirable material in the workpiece, for example, bones or fat in a meat portion.
The data and information measured/gathered at the scanning station is transmitted to a computer, preferably on board the portioning apparatus, which records the location of the workpiece on the infeed conveyor as well as the shape and other parameters of the workpiece. With this information, the computer determines how to optimally cut or portion the workpiece at the portioning station. Once the workpieces are scanned, they may be transferred to a cutting conveyor, typically composed of a metal mesh material. The portioning may be carried out by various types of cutting/portioning devices.
The cutting devices rely on the determined location of the workpiece on the belt at the scanning station to know where to make the cuts determined by the computer. Thus, it is important that the speed of the infeed conveyor and the cutting conveyor be accurately controlled, and ideally both conveyors will operate at the same, uniform speed. If the speeds of the conveyor vary, then the actual position of the workpiece relative to the cutting/portioning devices will not correspond to that calculated by the computer.
In addition, typically the metal belt of the cutting conveyor is driven by sprockets that engage the side margins of the belt, composed of formed flat wire. This type of drive introduces substantial variability in the speed that the cutting belt is driven. With each tooth of the sprocket engaging and disengaging the belt, the speed of the belt increases and decreases because of the variation in the pitch of the flat wire belt.
Also, natural belt resonance can set up oscillations or vibrations in both the infeed and the cutting belts, thereby causing the belt speeds to change. The present invention seeks to dampen oscillations and vibrations in the belts, as well as operate the belts at a constant speed and further reduce disturbances to the workpiece to be portioned as it is transferred from the infeed belt to the cutting belt.